In modern video game controllers, for example, the conventional way to detect motion is by measuring capacitance. One such motion detector 10 based on capacitance measurements is shown in FIG. 1. The motion detector 10 includes two metal plates 12, 14 separated by a small distance D. One of the plates is fixed and the other is free to move relative to the other in the direction illustrated by the arrow in response to some force. Some form of spring, such as bellow or diaphragm 16, is disposed between the two metal plates 12, 14 to restore the plates to their static relationship after a force induced motion of the two plates relative to one another. If there is a motion, the distance between the two metal plates 12, 14 will change from D to D′. The slight difference between D′ and D will result in a change in the capacitance between the two metal plates. By measuring the capacitance during the course of motion, the acceleration, the velocity and the distance of motion can be calculated. The motion sensors in Nintendo's WHO game controller are based on this principle.
The capacitance of the capacitor 10 is C=x*y*∈/D, where x and y are the two dimensions of the metal plates 12, 14, ∈ is the permittivity of the dielectric between the plates 12. 14, and D is the distance between plates. With these types of prior art motion detectors, the change in capacitance is very small and hard to measure in real time. An alternative motion sensor that is faster, cheaper, and/or more accurate is desired.